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Old   December 15, 2008, 08:59
Default MRF problem
  #1
Amir
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Hi,

In my case there is one vertical axis wind turbine consist of 10 vertical blades which is rotating with constant speed.

I placed this turbine inside one cylinder with the same radius as turbine base. I sketched the second cylinder which contains the first one with the same shape but with bigger radius.

these two cylinders are specified as an interior. these two cylinders are specified as one fluid in Gambit and will be specified to rotate with constant speed in Fluent as a MRF.

After running simulation its demonstrated that the inner side cylinder is acting not like an interior.

I need help to understand what the problem is.

I appreciate your concentration.

Regards.
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Old   December 16, 2008, 07:57
Default Re: MRF problem
  #2
Magic
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Amir,

How are the inner and outer cylinders connected? Did you subtract the inner form the outer? Are they connected? Please provide more detail of your geometry creation process?

Thanks

Khan
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Old   December 17, 2008, 14:44
Default Re: MRF problem
  #3
Amir
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I subtract the turbine from the inner cylinder and I split the outer and inner cylinder to each other. They are connected to each other.

Thanks

Amir
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Old   December 17, 2008, 20:57
Default Re: MRF problem
  #4
Yasser Selima
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I don't understand why did u use two cylinders. You can subtract the turbine from the outer cylinder and then you will have only one cylinder (interior) which should rotate on MRF.
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Old   December 18, 2008, 08:17
Default Re: MRF problem
  #5
Amir
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Hi.

I was wonder if the cylinder radius which will turn by MRF is bigger the results are more accurate. I can generate mesh just if I have the inner cylinder. in this way I can generate mesh using cooper method however, without inner cylinder the geometry is different and whatever I tried I couldn't generate mesh.

Amir,

Regards.
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Old   December 29, 2008, 02:25
Default Re: MRF problem
  #6
Milind Khedkar
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I do agree with Yasser. No need to generate two different cylinders. Give MRF only to one cylinder. Milind..
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Old   December 29, 2008, 08:19
Default Re: MRF problem
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Amir
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Dear Milind,

I would like to ask if the size of cylinder affects the results!

Regards.

Amir
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Old   December 29, 2008, 09:04
Default Re: MRF problem
  #8
Milind Khedkar
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No. The size of the cylinder will not affect the results if there is no stationary part enveloped within it. Also you can extend the outer boundary of the cylinder a bit. You have to maintain it as close as possible.

Milind..
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Old   December 30, 2008, 08:11
Default Re: MRF problem
  #9
Amir
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Dear Milind Khedkar,

Thanks for your respond. I will try again to see how far the results will change.

I would like to ask also the differences between MRF and Moving Mesh, and if I should use the Moving mesh instead of MRF.

I appreciate your concentration.

Amir.
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